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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5782_Библиотеки_им_академика_М_И_Перельмана.pdf
CHAPTER 6 Liver Scanning Protocol 99
common bile duct. Here, it divides into the gastroduodenal
artery and the proper hepatic artery.
• The proper hepatic artery divides into two main branches, the
right and left hepatic arteries which supply the right and left
segmental lobes, respectively.
• The middle hepatic artery generally arises from the left hepatic
artery.
• The cystic artery arises from the right hepatic artery.
(b) Hepatic veins: The right, middle, and left hepatic veins drain the
blood from the liver and empty it into the IVC.
(c) Portal vein: The main portal vein enters the liver at the porta hepa-
tis, posterior to the hepatic artery and common bile duct. It then
divides into the right and left branches. These branches become
intersegmental veins that branch into medial and lateral portions
of the left lobe and anterior and posterior portions of the right lobe.
(d) Portal venous system: Supplies the greatest percentage of total
blood flow to the liver. Formed by the confluence of three
tributaries:
(1) Splenic vein
(2) Superior mesenteric vein
(3) Inferior mesenteric vein
Commonly referred to as the portal splenic confluence. This system
carries blood from the spleen and bowel to the liver.
(e) Hepatic ducts: Enzymatic bile is manufactured in the liver then
transferred via the right and left hepatic ducts from the liver to the
extrahepatic bile ducts at the porta hepatis. As the right and left
hepatic ducts emerge from liver parenchyma at the porta hepatis,
they unite to form the common hepatic duct, which courses inferomedially where it is joined by the cystic duct to form the common
bile duct. The common bile duct descends to cross behind the first
portion of the duodenum to enter into or run along the posterior
portion of the parenchyma of the head of the pancreas. From there
it courses slightly toward the right and enters the second portion
of the duodenum, where it ends at the ampulla of Vater. The extrahepatic bile ducts (common hepatic, cystic, common bile) maintain communication between the liver and gastrointestinal tract.
(f) Portal triad: Refers to the proper hepatic artery, common duct, and
portal vein at the level of the porta hepatis. When there is a question of dilated bile ducts, a distinction between these structures
is important. The following oblique, transverse scanning plane
image shows that at the level of the porta hepatis, the portal vein
(1) lies posterior to the proper hepatic artery (2), which is on the
left and the common duct (3), located on the right. The appearance of the axial sections of the portal triad is often referred to as
“Mickey’s sign” as they resemble a face and two ears.
100 PART III Abdominal Scanning Protocols
Posterior
Anterior
Right Left
PORTAL
TRIAD
(From Brant WE: The Core Curriculum: Ultrasound.
Lippincott Williams & Wilkins, 2001.)
23
1
Physiology
• Vascular Functions: The vascular functions of the liver include
the storage and filtration of blood. The liver expands to act as a
blood reservoir in times of excess blood volume and supplies extra
blood in times of diminished blood volume. Kupffer cells that line
hepatic sinuses cleanse the blood of up to all but approximately
1% of bacteria found in portal blood from the intestine. It detoxifies drugs such as alcohol and barbiturates.
• Metabolic Functions: The liver is a primary center of metab-
olism, supporting multiple body systems and activities. It assists
the digestive and excretory systems by metabolizing fats, carbohydrates, and proteins to form bile and urea and in the process synthesizes many substances that are sent to other areas of the body
to perform a vast number of body functions. The liver uptakes
and stores glycogen, vitamins, and iron. It also forms most of the
substances utilized in blood coagulation and excretes drugs, hormones, and other substances into bile and ultimately the feces.
• Secretory and Excretory Bile Functions: Produces and
secretes bile through the biliary tract (ductal path) into the small
bowel where it is used for the digestion of fat.
CHAPTER 6 Liver Scanning Protocol 101
va
Posterior
Anterior
Sonographic Appearance
• As seen in the following image, the normal liver is described as
homogeneous, with midgray to moderately echogenic parenchyma.
Portions of blood vessels that appear anechoic may be seen scattered
throughout liver parenchyma. Normal liver parenchyma is generally
described as hyperechoic compared to normal renal cortex, as seen
in this image, and hypoechoic compared to the normal pancreas.
Liver
Right kidney
• Hepatic vessels and ducts display anechoic lumens surrounded by
variations of bright, echogenic walls. The next image shows how
portal veins and hepatic veins appear as anechoic, tubular structures branching throughout the liver. It is important to be able
to distinguish portal veins from hepatic veins. Some sonographers
use the difference often noted in the sonographic appearance of
their walls. Typically, as demonstrated in the image, portal vein
walls appear highly echogenic due to the reflective collagen that
encases them, while the walls of hepatic veins appear as if they
have no distinguishable margins because their walls contain minimal collagen. Note that this, however, is not a reliable way to make
the distinction between these two vessels, because smaller portal
vein branches may lack these surrounding echoes and in some
cases, bright, reflective walls have been visualized surrounding the
larger hepatic vein tributaries. These vessels have different branching patterns as well. Therefore, to correctly differentiate between
portal veins and hepatic veins, follow their branches back toward
the porta hepatis or IVC, respectively.
LeftRight
Inferior vena ca
102 PART III Abdominal Scanning Protocols
Posterior
Hepatic
m
ncreas
Hepatic
vena cava
y
Anterior
Posterior
Portal vein
branchs
Portal vein
Hepatic
vein
Liver
Inferior
vena
cava
Left
Diaphrag
Hepatic
vein
branch
Portal
vein
branch
Right
Hepatic
vein
branch
Portal
vein
branch
Diaphragm
vein
branch
Anterior
(Left image courtesy Ultrasoundpaedia.com.)
• The ligaments and fissures of the liver appear highly reflective due to
the fat and collagen within and around them. In the images below,
A, shows the bright, reflective ligamentum venosum and B, demonstrates the thin, bright main lobar fissure.
vein
Superior Inferior
Liver
caudate
lobe
Ligamentum venosum
A
Main lobar fissure
Right portal vein
Right lobe
B
of liver
Superior
Diaphragm
Inferior
Liver left lobe
Anterior
Posterior
Bare area
Ligamentum
venosum
Right renal
artery
Pa
Portal
vein
Gallbladder
Upper pole
of right kidne
Inferior
CHAPTER 6 Liver Scanning Protocol 103
Normal Variants
• Reidel’s lobe: Inferior extension of the right lobe.
• Absence of left lobe: Very rare. Results from occlusion of the left
hepatic vein due to abnormal extension of neonatal spasm of the
ligamentum venosum.
• Multiple size and shape variations.
Preparation
Patient Prep
• The patient should fast for 8 to 12 hours before the study. This
ensures normal gallbladder and biliary tract dilatation and reduces
the stomach and bowel gas anterior to the pancreas. This is significant because the liver, biliary tract, gallbladder, and pancreas are
interdependent systems.
• If the patient has eaten, still perform the examination.
Transducer
• 3.0 MHz or 3.5 MHz.
• 5.0 MHz for very thin patients. It may be necessary to use 5.0 MHz
for a patient’s left lobe and 3.0 or 3.5 MHz for the right lobe.
Breathing Technique
• Deep, held inspiration.
NOTE: Different breathing techniques should be used whenever the
suggested breathing technique does not produce the desired results.
Patient Position
• Supine.
• Left lateral decubitus, left posterior oblique, sitting semierect to
erect or prone as needed.
NOTE: Different patient positions should be used whenever the suggested position does not produce the desired results.
104 PART III Abdominal Scanning Protocols
T)
Pat
Liver Survey Steps
Liver • Longitudinal Survey
Sagittal Plane • Transabdominal Anterior Approach
NOTE: While you are scanning, experiment using different amounts of
transducer pressure (keeping patient comfort in mind) to improve imaging.
1. Begin to scan the liver with the transducer perpendicular, at the
midline of the body, just inferior to the xiphoid process of the
sternum. Have the patient take in a deep breath and hold it.
The general area of the left lobe should come into view as the most
anterior structure in the image. Identify the ligamentum venosum,
caudate lobe, and IVC or aorta.
Transducer
Patient’s left (L
ient’s right (RT)
NOTE: Depending on liver shape and patient respiration, varying
degrees of subcostal and inferior angles may have to be used when
scanning the liver longitudinally to completely survey the liver margins.
In some cases intercostal scanning will be necessary.
2. While viewing the left lobe, use subcostal angles and very slowly
move the transducer to the patient’s left, lateral and inferior along
the costal margin until you have evaluated the entire left lobe.
Note the aorta posteriorly.
RT
LT
CHAPTER 6 Liver Scanning Protocol 105
3. Return to midline just inferior to the xiphoid process to begin
evaluating the right lobe. Use subcostal angles and slowly move
the transducer to the patient’s right, lateral and inferior along the
costal margin until you are beyond the right lateral, inferior lobe.
You should be able to identify the IVC, hepatic veins, portal vein,
portal triad, porta hepatis, main lobar fissure, bile ducts, gallbladder (dilated or collapsed), right kidney, and perinephric space.
RT
LT
RT
LT
4. Move the transducer back onto the right lateral inferior lobe. Place
the transducer at the most lateral edge of the right costal margin
and use a very sharp subcostal angle to view the right lateral superior lobe. Move or angle the transducer right lateral and sweep
through and beyond the right lateral superior lobe. Identify the
dome of the right lobe and adjacent pleural space.
LT
RT
106 PART III Abdominal Scanning Protocols
NOTE: Even with sharp subcostal transducer angles the longitudinal
views of the right lateral superior lobe in a sagittal plane can be difficult
to visualize. As an alternative, try sagittal plane intercostal scanning or
scanning in the coronal plane from the patient’s right side.
Alternative 1: Right Lateral Superior Lobe of Liver •
Sagittal Plane • Intercostal Approach
Patient position: Supine, left posterior oblique or sitting semierect to erect
1. Begin scanning with the transducer perpendicular in an intercostal space anterior to the area of the right lateral superior
lobe. Suspended respiration may make the area easier to view.
2. Move the transducer to adjacent intercostal spaces to evaluate
the entire right lateral superior lobe.
3. Angling the transducer within the intercostal spaces and using
different breathing techniques can aid evaluation.
4. Note the dome of the right lobe and the adjacent pleural space.
LT
RT
Alternative 2: Right Lateral Superior Lobe of Liver •
Coronal Plane • Right Lateral Subcostal Approach
Patient position: Supine, left posterior oblique, left lateral
decubitus, sitting semierect to erect
1. Begin scanning at the mid coronal plane with the transducer
angled subcostal from the inferior costal margin.
2. With the patient holding their breath, vary the degree of the
transducer angle until all of the margins of the right lateral
superior lobe have been evaluated.
3. Note the dome of the right lobe and the adjacent pleural space.
LT
RT
CHAPTER 6 Liver Scanning Protocol 107
Alternative 3: Right Lateral Superior Lobe of Liver •
Coronal Plane • Right Lateral Intercostal Approach
Patient position: Supine, left posterior oblique, left lateral
decubitus, sitting semierect to erect
1. Begin scanning with the transducer perpendicular, midcoronal
plane, just inferior to the costal margin. Move superiorly into
the first intercostal space.
2. Have the patient use suspended or deep, held respiration, as
you move the transducer superiorly through the adjacent intercostal spaces until you scan through and beyond the right lateral superior lobe.
3. Angling the transducer within the intercostal spaces and using
different breathing techniques can aid evaluation.
4. Note the dome of the right lobe and the adjacent pleural space.
LT
RT
LT
RT
Liver • Axial Survey
Transverse Plane • Transabdominal Anterior Approach
1. Begin the axial evaluation of the liver with the transducer perpendicular, at the midline of the body, just inferior to the xiphoid
process of the sternum. Have the patient take in a deep breath and
hold it. The general area of the left lobe can be identified as the
largest and most anterior structure in the image. Identify the ligamentum venosum, caudate lobe, hepatic vein(s), IVC, and aorta.
LT
RT
NOTE: Depending on liver shape and patient respiration, varying degrees
of subcostal and inferior transducer angles may have to be used when scanning the liver from the axial plane to completely evaluate the superior and
inferior liver margins. In some cases intercostal scanning may be necessary.
108 PART III Abdominal Scanning Protocols
2. While viewing the left lobe, slowly move the transducer inferior
until you scan through and beyond the left lobe. Note the portal
vein and ligamentum teres.
3. Depending on liver shape and size, all of the left lateral aspect of
the left lobe may be seen in its entirety from midline. If not, return
to midline, just inferior to the xiphoid process. Use subcostal and
inferior angles and move the transducer to the patient’s left, lateral
and inferior along the costal margin until you scan through and
beyond the left lobe.
LT
RT
RT
LT
4. Return to midline, just inferior to the xiphoid process. To evaluate the right lobe, use subcostal and inferior transducer angles
and very slowly move the transducer to the patient’s right, lateral
and inferior along the costal margin until you scan through and
beyond the right lateral inferior lobe. Identify the IVC, hepatic
veins, portal vein, portal triad, right and left portal branches, porta
hepatis, main lobar fissure, bile ducts, gallbladder, right kidney,
and perinephric space.
LT
RT
LT
RT